1. Technical Field
The present disclosure relates to integrated circuit manufacturing, and more specifically to the manufacturing of trenches emerging on a silicon layer and having at least their bottom coated with silicide.
2. Description of the Related Art
Silicide is a compound comprising silicon and electropositive atoms, such as for example monosilicides like (Pt, Ni, Ir)Si, or metal-rich phases like (Pd, Mg, Ca)2Si or (Co, Ti, Ru, Cr, Er)Si2.
Nickel silicide (NiSi) is a material especially used to form an ohmic contact between the silicon and a metal. For example, nickel silicide is interposed between the silicon of a source and of a drain of a MOS transistor and metal contacts forming the transistor terminals, which results in decreasing the resistance of access to the source and to the drain and in providing a better ohmic contact.
Usually, nickel silicide is obtained by bringing together platinum nickel (NiPt) and silicon and by performing an anneal which forms the nickel silicide.
The quality of the ohmic contact especially depends on the nickel silicide volume between the silicon and the metal contact, on the presence of impurities and of residue between these different materials and on the contact surface area between the different materials.
Some advanced CMOS technology transistor manufacturing methods, especially methods for manufacturing transistors having a gate width equal to or smaller than 28 nanometers, form silicide at the bottom of holes or trenches emerging on the drain and source areas (“Hole salicide”).
Now, the forming of holes generally is a source of impurities and of residue, mainly located at their bottom. Further, the forming of a nickel silicide layer having both a large volume and a large surface area at the bottom of the holes is more difficult as the form factor of the holes, that is, the ratio of the depth to their cross-section, increases.